The Extended Core Coax: A Novel Nanoarchitecture for Electrochemical Sensing of Infectious Disease Biomarkers*

We report the development and fabrication of a novel nanoarchitecture for electrochemical sensing, the extended core coax (ECC). Each ECC is a vertically oriented nanocoax, comprised of an extended inner metal core and an outer metal shield, separated by a dielectric annulus. The inner (gold) and outer (chrome) metals serve as the working and counter electrodes, respectively, with $\sim$200 nm separation gap / annulus. Arrays with a base area of 0.1 mm$^{2}$ were fabricated, each containing $\sim$10$^{5}$ individual ECCs connected in parallel. Previous iterations of the nanocoax have demonstrated $\sim$100x greater electrochemical response over a planar control due to the nanoscale proximity of the working and counter electrodes [1]. We anticipate the ECC will function similarly, and offer the additional benefit of overcoming diffusion limitations due to the extended core working electrode, which protrudes $\sim$200 nm above the shield of the ECC. Additionally, the extended gold core provides a substrate for biofunctionalization, making the ECC an attractive candidate for further development towards electrochemical detection of infectious disease biomarkers such as cholera toxin. \\[4pt] [1] B. Rizal, et al., Anal. Chem. 85, 10040 (2013).